Proactive Tool Discovery

When there are hundreds or thousands of tools, flat listing schemas in the prompt doesn’t work.

Approaches:

pre-selection via search;
proactive declaration – the agent describes the need in natural language itself (MCP-Zero, tool_search);
hierarchical matching – first the server, then the tool within it.

If no match is found – explicitly return “not found”, let the agent rephrase or create a tool.

The transition from passive “selection” to active “discovery” turns the tool selection problem into a knowledge retrieval problem.